This invention relates to thermoplastic polymer compositions which are thermoformable, and to thermoformed articles made from such compositions.
The compositions of the present invention, which are halogen-free, are useful for making laminates, sheets and films, and for replacing polyvinyl chloride (PVC) resins in many of their tradition uses. In particular, compositions of the present invention, and thermoformed articles made therefrom, are suitable as PVC replacements in the automotive field. They may be used in the fabrication of interior sheating of automobiles, for example, in the instrument panel skins, door panels, roof liners and seat covers.
Automotive applications require certain properties in the resins, including good flexibility, low temperature properties, capability of providing a soft surface texture and grain retention: as well as good high temperature properties and low emissions associated with it in view of the extreme temperatures the interior of automobiles can reach on hot, sunny days.
Non-halogenated thermoplastic compositions having good high temperature properties are known in the art, for example the polyolefin/ionomer blends disclosed in U.S. Pat. No. 4,871,810, or the blends of partially crosslinked ethylene/.alpha.-olefin copolymers with reaction products of ethylene copolymer ionomers and olefin/epoxy copolymers, disclosed in U.S. Pat. No. 4,968,752. Such compositions, however, are deficient in softness.
The deficiencies of the prior art compositions have been largely overcome by a composition comprising a blend of polypropylene, ethylene copolymer ionomer resin, ethylene/glycidyl acrylate or methacrylate copolymer, and uncrosslinked ethylene propylene rubber as described in U.S. Pat. No. 5,206,294. Such a blend has been proven suitable for most applications and it is characterized by good thermoformability and grain retention. These blends, however, are not calenderable. The presence of ionomer resin and ethylene/glycidyl acrylate or methacrylate copolymer leads to excessive sticking of the blend on metal rolls of the processing equipment. As certain processors are equipped only with calendering equipment. As certain processors are equipped only with calendering equipment (not with extrusion equipment) there is a commercial need for thermoplastic polymer blends suitable for making thermoformed articles by calendering, which articles demonstrate the requisite flexibility, temperature properties, capability of providing a soft surface texture and grain retention for automotive applications.